This invention relates to wireless electronic devices and more particularly, to ways of operating wireless electronic devices in a radio-frequency communications network.
Electronic devices such as handheld electronic devices, portable electronic devices, and computers are often provided with wireless communications capabilities. Electronic devices with wireless communications capabilities typically include antennas that serve to transmit and receive radio-frequency signals.
It may be desirable to incorporate more than one antenna in a single electronic device. Electronic devices with more than one antenna may be referred to as multi-antenna devices. A multi-antenna device may exhibit performance improvements over a single-antenna device. For example, in comparison to a single-antenna device, a multi-antenna device may have a higher antenna gain and increased capacity. As a result, multi-antenna devices have been developed for use in a wireless communications system. A communications system in which radio-frequency signals are conveyed between two multi-antenna devices may be referred to as a multiple-input and multiple-output (MIMO) system or a multiple antenna system (MAS).
A conventional MIMO communications network typically includes base transceiver stations (or base stations) that are positioned at different geographical locations. A group of antennas and associated radio-frequency equipment are placed adjacent to each base station. The group of antennas located at each base station serves to provide a radio coverage area for that base station. The radio coverage area served by each base station is commonly referred to as a cell. The base stations in the conventional communications network are therefore sometimes referred to as cell sites.
Placing antennas at a centralized location within each cell may be convenient but often does not provide satisfactory coverage particularly at the cell edges. As an example, consider a scenario in which a user device is moving further away from a current serving base station. As the distance between the mobile user device and the group of antennas located at the current serving base station increases, maintaining an active data connection with that base station may become increasingly difficult for the user device (i.e., transmit/receive performance degrades at cell boundaries).
Consider another scenario in which a user device is currently moving within an urban setting having physical variations in the terrain between the user device and the base station. For example, there may be buildings, moving cars, and other obstacles capable of creating coverage holes (i.e., portions in the cell that exhibit substantially degraded service due to the presence of physical obstacles) in the cell. If the user device moves into one of these coverage holes, any data connection between the user device and the serving base station may be terminated.
It may therefore be desirable to provide methods for operating an electronic device in an improved wireless communications network.